Gyimah’s resignation came hours after UK Prime Minister Theresa May had said that the UK government would end talks with the EU on Galileo, and would instead consider building its own global satnav system for use after Brexit.

That idea was first floated by the government in May, but many experts have dismissed it as too expensive, unnecessary and even unfeasible — the lack of available space on the radio spectrum to run such a system could be a show-stopper.

Nature digs into the dispute.

What did the science minister say about Galileo when he resigned?

Gyimah resigned in protest at the Brexit divorce agreement reached last month by the United Ki﻿ngdom and the EU, and over discussions about Galileo. He said that the EU’s superior hand in negotiations over the programme convinced him that Britain would fare badly in future negotiations on many other issues, including research, should the divorce deal go ahead. (The deal prompted a spate of other ministerial resignations, and its fate is currently uncertain.)

What is Galileo, and why is it so important?

Galileo is one of four global satnav systems, which provide myriad civilian, scientific and defence servicess. The others are the US Global Positioning System (GPS), Russia’s Global Navigation Satellite System (GLONASS) and China’s BeiDou, which will be fully operational in 2020. The EU started the Galileo programme in 1999 to break its dependence on GPS and GLONASS.

The Galileo constellation — comprising 26 satellites — was completed this July; a near-complete constellation began beaming down signals free of charge to smartphones and other receivers in December 2016.

Most modern satnav receivers combine signals from all four systems to increase accuracy and reliability. Researchers also combine signals and use them in an array of scientific applications, including the monitoring of movements in Earth’s crust and studying the atmosphere.

The Galileo programme is building another 12 satellites as in-orbit spares and to replace older craft. It is also starting to build a next-generation system that would come into service around the middle of the next decade. The EU opened the first of the tenders for building these craft in June.

Who paid for Galileo and how much did it cost?

The project is funded through the EU’s budget. Total costs are estimated at around €13 billion (US$15 billion) to €15 billion to the end of 2020.

How would Brexit change the United Kingdom’s participation in Galileo, and why is the UK government unhappy?

Brexit itself would have no effect on the availability of Galileo signals to scientists and other UK citizens — the service is freely available to anyone on the planet.

But a UK-based company, Surrey Satellite Technology (SSTL) in Guildford, a subsidiary of the aerospace giant, Airbus, made all the satellites built so far — although many components, such as the satellites’ atomic clocks, are sourced from suppliers in Europe.

After Brexit day on 29 March next year, the UK would enjoy a transition period until the end of 2020 during which relations in many areas would stay much the same. But the EU has already effectively excluded UK companies — and therefore SSTL — from bidding for the lucrative tender for the next-generation satellites. It also ignored a plea by Gyimah to postpone the tender to allow more time to seek an arrangement.

The UK government complains that this treatment is unfair given that it has so far contributed around 12% of Galileo’s budget — about €1.4bn.

But economically, the UK has been a net beneficiary of the project, points out Bleddyn Bowen, an expert in international affairs at the University of Leicester who has studied the impact of Brexit on space policy. The country has won back some 17–19% of Galileo’s total budget in industrial and research contracts. These returns have in turn strengthened the UK space industry’s science and engineering capabilities, he adds.

The UK government is also unhappy that after Brexit day, under EU rules, it automatically stops having access to or being involved in the defence-related and classified aspects of the Galileo programme — something it had hoped to remain a part of.

What are Galileo’s defence applications?

The system’s secure service, scheduled to be fully operational by﻿ around 2026, would be restricted to government-authorized users, including the military and essential services such as energy companies and telecoms. The signals are encrypted to control access and to stop interference or malicious jamming.

The United Kingdom has been closely involved in the secure system’s development, and built much of the related cryptographic equipment. It argues that this close participation, and the UK’s significant role in EU defence matters, mean it should be given special treatment allowing it a full role in the inner workings of Galileo’s defence aspects and its industrial pay-offs.

The EU had said that the United Kingdom could apply to access the encrypted signals after Brexit, as is possible under a 2011 EU law for third-party access; the United States and Norway have already applied. But EU rules (which the United Kingdom helped to draft) do not allow a non-member state to be involved in continued research, development and procurement of the security aspects of Galileo.

The United Kingdom said that this is unacceptable, leading May to say earlier this month that the government would abandon plans to use Galileo for defence and critical national infrastructure. She also confirmed that the United Kingdom was looking at options for building its own global system.

Is that proposal credible?

It might be technically feasible, say experts — the United Kingdom has the science and engineering skills to build such a system — but it probably isn’t affordable.

Widely cited estimates put the cost of building a system at somewhere between £3 billion (US$4 billion) and £5 billion. That doesn’t include the running costs, which amount to about €800 million a year for Galileo. For comparison, the UK space agency’s budget this year is £402 million, and entire UK defence research budget will be about £1.9 billion next year.

“Spending £3 billion to £5 billion on a UK system would be grotesquely wasteful,” says Robert Massey, deputy executive director of the UK Royal Astronomical Society in London.

The money would be better spent on more-pressing UK defence priorities and industries in space, rather than on duplicating what already exists, says Bowen.

In August, the UK government said that it was setting aside £92 million to design the proposed system. That sum alone exceeds the UK budget for basic astronomy research, says Massey.

But even if Britain were to build its own system, there could be a crucial technical limitation: the lack of suitable space on the radio spectrum.

What’s the issue with the radio spectrum?

The four existing global satnav systems already take up the part of the spectrum allocated for satellite navigation by the International Telecommunication Union (ITU), which regulates spectrum allocations, says Alexandre Vallet, head of the ITU’s Space Services Department in Geneva, Switzerland.

Squeezing a new global system into this spectrum would require novel radio-signal designs that don’t interfere with other systems, says Vallet. And these would need to be endorsed by international agreements.

Failing that, Britain﻿ could request an ITU World Radiocommunication Conference — a meeting held to review and revise the international treaty governing the use of the radio-frequency spectrum — to allocate more spectrum for satnav systems, says Vallet.

But that part of the spectrum is already under heavy demand from many other applications, such as mobile phones and aeronautical and military radars, so it would still be a challenge to make room for another global satnav system, he says. Such a move would also need Britain to gather considerable support from other countries, he adds.

How is this likely to play out?

After Brexit — whatever form it takes — the EU is likely to consider the UK as a third country in Galileo, says Federico Santopinto, a researcher at the Brussel-based Group for Research and Information on Peace and Security — so involvement in developing the secure programme would be off the table. The EU will probably eventually allow the United Kingdom to receive Galileo’s secure signals but entirely on its terms, he says.

Nature564, 172-173 (2018)

doi: 10.1038/d41586-018-07734-x

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